System for inspection of pipelines

ABSTRACT

A system for inspecting pipelines, especially in the coupling between pipe parts, comprises a radiation source and a detector device or a photographic film. The pipeline includes indicators which are laid into the pipeline material and have a differing absorption of radiation than the material comprising the layers of the pipeline in which the indicators are formed. By placing the radiation source and the detector device (or photographic film) on opposite sides of the pipeline, or on opposite sides of a wall of the pipeline, the position of the indicators may be detected, and any displacement can be measured.

FIELD OF THE INVENTION

The invention relates to a system for inspection of pipelines,especially the coupling between parts of the pipe, comprising an x-raysource, a detector device for detection of x-rays, possibly aphotographic film being sensitive in the x-ray range, adapted to receivethe radiation and to be positioned on the opposite side of the pipe wallor pipeline in relation to the source.

BACKGROUND OF THE INVENTION

Pipelines being used in the oil and gas field are often subject to largestrain in the form of stress, pressure and temperature variations.Because of this the pipelines are frequently inspected fordisplacements, cracks or possible leaks. A known method for performingsuch inspections is x-ray photographing of the pipeline. Differentsystems performing such inspections are available on the market.

Flexible pipelines are built to stand the abovementioned strains. Ausual structure of flexible pipelines is a multi-layer system of steelpipes with polymer materials between them. The polymer layers include apressure sheet which hinders diffusion and leakage of the pipelinecontent out into the environment. It is also demanded that the pressuresheet is able to move relatively freely in relation to the steel pipes,thus not to be subject to unnecessary strain when the pipeline moves.Between the pressure sheet and the steel pipes an anti-creep sheet isoften placed in order to keep the pressure sheet from fastening to thesteel layers. In the ends of each pipe part a coupling part is comprisedwhich among other things may comprise a sealing or a packing ringproviding a seal between the pipelines and also between the pressuresheets.

A problem relating to the abovementioned structure is that the pressuresheet has shown a tendency to contract and thus be drawn away from thesealing ring, making the pipeline leaky.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system to be ableto detect relative displacements between parts in a pipe system. It isespecially preferred to provide a system being capable of detecting andmeasuring displacements in polymer layers or the like between steellayers in a pipeline, especially in the vicinity of the coupling pointsbetween the different pipe elements.

The present invention is a system for inspecting movable or deformablelayers in pipelines, comprising an x-ray radiation source positioned onone side of a pipeline or a wall of the pipeline, a detector device or aphotographic film adapted to receive radiation and positioned on theopposite side of the pipeline wall or the pipeline in relation to theradiation source. The pipeline comprises at least a first material layerand a second material layer and at least one movable or deformable thirdmaterial layer positioned between the first and second material layers,the third material layer being softer than the first and second materiallayers. The third material layer includes indicators, the indicatorshaving a differing absorption of radiation from the third materiallayer.

The invention may further be defined wherein the indicators have alength larger than their thickness or width.

Further, the indicators may comprise wires or strings of a fourthmaterial, the wires or strings having a thickness approximately onethird of the thickness of the third material layer.

The pipeline in the present system may include more than two materiallayers that are harder than the third material layer. The more than twolayers are alternating and separated by different ones from a pluralityof third material layers. At least two of the third material layersinclude indicators.

Further, the indicators in each of the third material layers may have adifferent shape.

Imaging of the pipeline in the present invention may be performed from aplurality of directions, and a tomographic picture of the pipeline maybe made from this imaging.

The pipeline may comprise coupling points between two parts of thepipeline. The pipeline at each of the coupling points may comprise oneor more sealing rings, the sealing rings including indicators.

Each third material layer of the present invention may comprise one ormore layers of different materials, these layers of different materialsforming pressure sheets or anti-creep sheets.

Another embodiment of the present invention is a pipe section comprisinga first material layer, a second material layer and at least one movableor deformable third material layer. The third material layer ispositioned between the first and second material layers and is softerthan the first and second material layers. The third material layerincludes indicators having a differing absorption of radiation from thethird material layer.

Yet another embodiment of the present invention is a method forinspecting movable or deformable layers in pipelines. The methodcomprises the steps of positioning an x-ray radiation source on one sideof a pipeline or a wall of the pipeline and detecting radiation on theopposite side of the pipeline wall or the pipeline in relation to anx-ray radiation source. The pipeline comprises at least a first materiallayer and a second material layer and at least one movable or deformablethird material layer. The third material layer is positioned between thefirst and second material layers and is softer than the first and secondmaterial layers. The third material layer includes indicators having adiffering absorption of radiation from the third material layer.

This way a simple system is obtained for inspecting pipelines beingmainly based upon already available equipment, the implementation ofwhich in new (and existing) pipe systems being easy and relativelycheap.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to a preferredembodiment shown in the enclosed figures.

FIG. 1 shows a cross-section of the system for inspecting the end of apipe, as seen from one side.

FIG. 2 shows a sketch of a system corresponding to the system shown inFIG. 1, as seen from above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 and FIG. 2 illustrate an inspection of the pipe end 2 in apipeline 1 comprising a polymer layer 5 being positioned between twosteel layers 8,9. The pipe end also comprises a sealing or packing ring7 for tight coupling to another pipe element. In the polymer layer 5marks or indicators 11,12 are placed, being made from a material havinga higher dampening than the rest of the material in the pipeline, e.g.platinum or tungsten. Preferably these reference points have a knownposition. In this way reference points in the polymer layer 5 areobtained which may be seen by x-ray photography of the pipe end 2, andwhich thus may indicate a displacement of the polymer layer in relationto the steel layers. Thus, it may be discovered if the pressure sheetshrinks and moves past the seal 7. Preferably there are structures inthe steel layers 8,9, possibly provided for other purposes, e.g.recesses for the sealing ring, which may serve as reference points sothat movements in the polymer layer in relation to the steel layers maybe measured easily.

In a preferred embodiment of the invention the indicators/marks 11,12have oblong shapes and are positioned with a chosen orientation in thepolymer layer 5 so that its position may be determined more easily. Inthe figures the indicators are given axial 11 and tangential 12orientations, respectively. Intermediate orientations may of course alsobe chosen. In certain cases a radial orientation may also be chosen,which will provide an improved possibility for detecting squeezing anddeformations in the polymer layer.

The most simple way to produce the indicators 11,12 may be from stringsor wires by cutting them in desired lengths. The thickness of the wiresmay be chosen depending on the dimensions of the pipeline and thethickness of the polymer layer, and may also depend on the relationshipbetween the x-ray absorption of the indicators and of the pipeline. In apreferred embodiment the indicators have a thickness of approximately ⅓of the thickness of the polymer layer. Used in the oil and gas relatedactivities, the indicators are preferably made from a corrosionresistant material.

The polymer layer will, as mentioned above, often comprise more than onelayer, usually with a pressure sheet hindering leaks and diffusion ofthe pipelines contents and an anti-creep sheet stopping the pressuresheet from sticking to the steel layer. The indicators may be placed inone or more of these layers.

The x-ray imaging of the pipeline may be performed by using differenttypes of well-known equipment, e.g. based upon cobalt sources, linearaccelerators or corresponding high energy sources, preferably in therange of MeV, but the requirements to the source will of course dependon the materials used in the pipeline.

To detect the radiation and provide a picture of the pipeline, suitabletypes of photographic film may be used. Electronic detectors and imagingdevices may, however, also be used. Neither the choice of source nor thechoice of imaging unit are important to the present invention other thanthe obvious choices relating to the materials in the pipeline, thedesired intensity, etc, that need to be made in order to obtain asufficiently sharp picture with sufficient contrast.

In the figures a method is illustrated in which a photographic film 4 isplaced inside the pipe and the source 3 is outside the pipe. In anembodiment of the present invention several pictures are taken atdifferent angles, which are combined electronically to, with availablesoftware, to provide a tomographic picture of the pipeline.

In another embodiment of the invention the source 3 and the film 4 orimaging device are positioned outside, and on either side, of thepipeline. Using tomographic techniques a complete picture of thepipeline and the possible displacements of the indicators may beobtained. This solution may also give an opportunity to inspect thepipeline in its full length, possibly without disassembling thepipeline. If this method for measuring is to be used, it may, under somecircumstances, be topical to place the indicators along the whole lengthof the pipeline.

The figures show a simplified version of a pipeline. As mentioned abovethe pipeline 1 will comprise several types of polymer layers, pressuresheets and anti-creep sheets, and layers of steel or correspondingmaterials. The indicators in the different layers may be placed withvarying positions or orientations depending on in which layer they are,or possibly with other, more complex shapes in order to provide aclearer view showing which layers are out of place. In such complexpipelines tomographic method may be utilized advantageously.

In another embodiment of the invention the system according to theinvention may be used to control the position of the sealing or packingrings by laying the indicators 11,12 into it. If the pipeline comprisesmore than one sealing rings, the indicators may be placed in one or moreof them.

In another embodiment of the invention the system according to theinvention may also be utilized for inspecting pipelines that do notcomprise several layers, e.g. simple plastic or steel pipes. In thiscase the indicators may be positioned directly in relation to thepipeline material, e.g. in order to measure displacements between twocoupled parts of a pipeline.

The present invention may, as mentioned above, be used in relation topipelines in oil or gas related activities, but is not limited to this.Different pipe materials, radioactive or x-ray sources, detectors orimaging methods, and indicator-materials may be chosen depending on theparticular pipe system and the available equipment.

What is claimed is:
 1. A system for inspecting movable or deformablelayers in pipelines, comprising an X-ray radiation source positioned onone side of a pipeline or a wall of said pipeline, a detector device ora photographic film, adapted to receive radiation and positioned on theopposite side of said pipeline wall or said pipeline in relation to saidX-ray radiation source, said pipeline comprising at least a firstmaterial layer and a second material layer and at least one movable ordeformable third material layer positioned between said first and secondmaterial layers, said third material layer being softer than said firstand second material layers, wherein said third material layer includesindicators, said indicators having a differing absorption of radiationfrom said third material layer.
 2. A system according to claim 1,wherein said indicators have a length larger than their thickness orwidth.
 3. A system according to claim 2, wherein said indicatorscomprise wires or strings of a fourth material, said wires or stringshaving a thickness approximately one third of the thickness of saidthird material layer.
 4. A system according to claim 2, wherein theorientation of each of the indicators, when photographed with theradiation source, allows determination of the position of thephotographed structures.
 5. A system according to claim 1, wherein thepipeline includes more than two material layers that are harder thansaid third material layer, said more than two material layersalternating and being separated by different ones from a plurality ofthird material layers, and wherein at least two of said third materiallayers include indicators.
 6. A system according to claim 5 wherein theindicators in each of said third material layers has a different shape.7. A system according to claim 1, wherein imaging of the pipeline isperformed from a plurality of directions, and a tomographic picture ofthe pipeline is made from this imaging.
 8. A system according to claim1, wherein the pipeline comprises coupling points between two parts ofthe pipeline, the pipeline at each of said coupling points comprisingone or more sealing rings, said sealing rings including indicators.
 9. Asystem according to claim 1, wherein each third material layer comprisesone or more layers of different materials, said layers of differentmaterials forming pressure sheets or anti-creep sheets.
 10. A systemaccording to claim 1, wherein the pipeline comprises a number ofinterconnected pipes, and said indicators are positioned close to theends of the pipes.
 11. A system according to claim 1, wherein theindicators are made from a corrosion resistant material.
 12. A systemaccording to claim 5, wherein imaging of the pipeline is performed froma plurality of directions, and a tomographic picture of the pipeline ismade from this imaging.
 13. A system according to claim 5, wherein thepipeline comprises coupling points between two parts of the pipeline,the pipeline at each of said coupling points comprising one or moresealing rings, said sealing rings including indicators.
 14. A systemaccording to claim 5, wherein each third material layer comprises one ormore layers of different materials, said layers of different materialsforming pressure sheets or anti-creep sheets.
 15. A system according toclaim 5, wherein the pipeline comprises a number of interconnectedpipes, and said indicators are positioned close to the ends of thepipes.
 16. A system according to claim 5, wherein the indicators aremade from a corrosion resistant material.
 17. A pipe section comprising:a first material layer; a second material layer; and at least onemovable or deformable third material layer positioned between said firstand second material layers, said third material layer being softer thansaid first and second material layers and including indicators having adiffering absorption of X-ray radiation from said third material layer.18. The pipe section according to claim 17, further comprising: at leastone additional movable or deformable third material layer; and at leastone additional material layer that is harder than said third materiallayer, wherein said first, second and additional harder material layersalternate with and are separated by different ones from the plurality ofsaid third material layers, and at least two of said third materiallayers include indicators.
 19. The pipe section according to claim 17,further comprising coupling points on at least one end of pipe section,the pipe section at the coupling point comprising one or more sealingrings, said sealing rings including indicators.
 20. The pipe sectionaccording to claim 17, wherein each third material layer comprises oneor more layers of different materials, said layers of differentmaterials forming pressure sheets or anti-creep sheets.
 21. A method forinspecting movable or deformable layers in pipelines, comprising thesteps of: positioning an X-ray radiation source on one side of apipeline or a wall of said pipeline; and detecting radiation on theopposite side of said pipeline wall or said pipeline in relation to saidX-ray radiation source; wherein said pipeline comprises at least a firstmaterial layer and a second material layer and at least one movable ordeformable third material layer positioned between said first and secondmaterial layers, said third material layer being softer than said firstand second material layers; and wherein said third material layerincludes indicators, said indicators having a differing absorption ofradiation from said third material layer.
 22. The method as defied inclaim 21, wherein said positioning and detecting steps further includethe steps of positioning an X-ray radiation source and detecting theradiation therefrom in a plurality of different directions.